1. Field of the Invention
The present invention relates to an imaging technology, more particularly to a technology capable of being effectively applied to imaging devices, such as a complementary metal oxide semiconductor (CMOS) image sensor and the like.
2. Description of the Related Art
For example, compared with a charge coupled device (CCD) image sensor, a CMOS image sensor is well matched with peripheral image processing circuits in a manufacturing process, operating voltage and the like, and in the CMOS image sensor, an imaging device, an image processing circuit, a controller and the like can be easily integrated on one chip.
Since in this CMOS image sensor, not only an optical/electrical conversion device but a conversion signal can also be amplified at each pixel level, the CMOS image sensor has an advantage of being resistant to noise in the transmission process of an optically/electrically converted signal. However, the CMOS image sensor has fixed pattern noise due to the uneven characteristic of an amplifier at each pixel level, which is a problem.
In this case, as the countermeasure, a configuration in which the same number of correlation double sampling (CDS) circuits and analog/digital conversion (ADC) circuits as that of columns are arrayed in parallel for each set of pixels in the column direction of a plurality of pixels two-dimensionally arrayed in the orthogonal row and column directions, that is, a configuration for reducing the fixed pattern noise by a so-called column ADC method, is known.
However, in this column ADC method, an output image takes a vertical striped pattern due to unevenness (column offset) in an ADC circuit and the like among columns, which is another problem.
In order to offset the column offset, it is possible to duplicate the circuit configuration of a column ADC to offset the unevenness between the two systems. However, even in this case, the unevenness of the original main signal system, due to unevenness among devices composing each pixel cannot be offset.
As to the CMOS image sensor, for example, Patent Reference 1 discloses a technology for diagnosing/managing the operation of the entire image sensor using a state machine and solving the problem of a column CDS by digitizing a processing signal.
Patent Reference 1: Japanese Patent Application Laid-open No. 11-331883.